DESCRIPTION: Recent evidence indicates that animals with prior stress experience also exhibit behavioral sensitivity or hyper- responsiveness in later test situations. The applicant has recently demonstrated that rat pups isolated from the nest, dam and siblings for as little as one hour per day during the first week of life results in hyperresponsivity to an amphetamine challenge administered in adulthood. The applicant's primary hypothesis is that stress experienced early in life significantly alters neuronal plasticity within the CNS and results in permanent changes in brain function. In particular, the applicant has shown that neonatal stress enhanced LTP measures obtained from juveniles while earlier studies in stressed adults showed impairment of LTP. The applicant now proposes to examine the impact of neonatal stress upon both electrophysiological (LTP) and neurochemical (in vivo microdialysis) measures obtained from both male and female rats before and after tetanization of the medial perforant pathway.